Matter & Energy

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MEASURING UP This metal cylinder is the United States’ copy of the international kilogram kept in France. Scientists hope to replace this standard, the last physical object used to define a unit of the metric system, with a definition of mass based upon fundamental physical constants.

Robert Rathe/NIST/Flickr

BEND, BUT DON’T BREAK Folded layers of carbon nanotubes, seen under a scanning electron microscope, allow an elastic fiber to conduct electrical current when stretched.

The Alan G. MacDiarmid NanoTech Institute

CARBON CONFUSION Carbon released from fossil fuel burning will jeopardize the usefulness of many carbon dating applications, such as identifying illegal ivory, new research predicts.